Hercules Constellation Now Showing in Summer Night Sky

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With the bright moon out of the late evening sky early this week,
stargazers will be treated to views of the "celestial strongman"
in the night sky: the constellation of Hercules.

To spot the constellation of
Hercules, look high overhead at around 10 p.m. local time.
The star pattern of the traditional mythological figure is
difficult for modern skywatchers to visualize, but astronomer
Robert H. Baker (1880-1962) described its six brightest stars as
a "butterfly with outspread wings." Others sometimes describe
those same stars as outlining the initial "H" for Hercules.

In ancient times, however, primitive men seemed to have no
difficulty picturing these stars as forming the figure of a
kneeling man.

In about 260 B.C., the Greek poet Aratus noted that "... no one
knows how to read that sign clearly, nor on what task he is
bent."

Strongman or danceman?

Aratus referred to Hercules as a "phantom," and pointed out that
Hermes brought a Lyre into heaven (the nearby constellation of
Lyra) and set it in front of the unknown phantom near his left
hand.

Lyra was known to the Greeks as the first string instrument of
their bards. In fact, the Arabs called the kneeling phantom, "Al
Rakis, the Dancer," and also the "One Who Kneels On Both Knees."
The old Arabic name of its
brightest star, Ras Algethi, means "The Head of the Kneeler."

The poets from 22 centuries ago were actually singers and dancers
— the early bards danced and sang, accompanying themselves on the
harp with appropriate music. Some experts in mythology believe
that the constellation we now call Hercules may have originally
represented Thamyris, a son of the king Philammon whose main
avocation was to sing, dance and play the harp. [ Skywatching
Maps & Charts ]

So, exactly who
are these stars supposed to represent ? Was it really
Hercules, the half-mortal son of Zeus who was immensely strong
and revered throughout the Mediterranean? Or perhaps it was
Thamyris, who otherwise might have become known as the celestial
song and dance man of the sky?

The Great Cluster in Hercules

Within Hercules is quite possibly the most celebrated object in
the summertime skies: The
Great Cluster in Hercules, which is also known as M13. The M
represents the initial of the famed 18th century comet observer,
Charles Messier (1730-1817).

Messier was deeply interested in discovering comets but he was
plagued by the same trouble that besets all comet hunters: he
kept finding "comets" that were not comets at all, but star
clusters and nebulas. Messier's hopes were dashed so often that
for his own convenience, he kept a list of these deceiving
objects, which he published in a catalogue.

To locate Messier 13, look toward the four stars, known as the
"Keystone," which supposedly forms the body of Hercules. A
keystone is the stone atop an arch, and its shape is narrower at
one end.

It is between the two western stars of the keystone that we can
find the Great Globular Cluster of Hercules. It’s about a third
of the way along a line drawn from the stars Eta to Zeta.

Actually, it was not Messier, but Edmund
Halley (who discovered the famous comet of the same name),
who first mentioned it in 1715, having discovered it the previous
year: "This is but a little Patch," he wrote, "but it shows
itself to the naked Eye, when the Sky is serene and the Moon
absent."

A celestial chrysanthemum

Located about 25,000 light-years
away, the Hercules Cluster measures 160 light-years across,
and is estimated to be made up of a ball of tens of thousands of
stars.

Messier first saw the cluster in June 1764 and described it as a
"round and brilliant nebula with a brighter center, which I am
sure contains no stars."

Today, if you use good binoculars and look toward that spot in
the sky where M13 is located, you will likely see a similar view:
a vaguely round glow or patch of light.

Moving up to a telescope, the view dramatically improves. With a
4- to 6-inch telescope, the "patch" starts to become resolved
into hundreds of tiny pinpoints of light. In larger instruments,
Messier 13 is transformed into a spectacular celestial
chrysanthemum.

In his Celestial Handbook, Robert Burnham (1931-1993) describes
the view of the cluster in a 12-inch or larger telescope as, "...
an incredibly wonderful sight; the vast swarm of thousands of
glittering stars, when seen for the first time or the hundredth,
is an absolutely amazing spectacle."

Editor's note: If you have an amazing skywatching photo you'd
like to share for a possible story or image gallery, please
contact managing editor Tariq Malik at tmalik@space.com.

Joe Rao serves as an instructor and guest lecturer at New
York's Hayden Planetarium. He writes about astronomy for The New
York Times and other publications, and he is also an on-camera
meteorologist for News 12 Westchester, New York.